The long term goal of my research is to understand the regulation of pattern formation and morphogenesis in plants. The shoot apical meristem is responsible for the production of shoot-derived organs throughout plant development. Elucidation of the molecular and cellular mechanisms that are involved in meristem function is critical to understand how these self- organizing centers dictate plant architecture. The maize inflorescence is a useful model for the study of meristem function because it contains several different reproductive meristem types. I will begin by studying a developmental switch point which restricts the fates of branch meristems in the developing inflorecence. Mutations in the ramosa 2 (ra2) gene affect this developmental switch point. I propose to clone the ra2 gene using a PCR-mediated approach. The function of this gene will be investigated by examining the gene and protein expression domains in situ. The effect of ra2 on the expression of other genes known to be expressed in the branch or spikelet meristems will also be investigated. The genetic interaction between rat and genes which also effect tassel architecture will be analyzed by double mutant analysis to place ra2 within a genetic network. Finally, transgenic lines of Arabidopsis ectopically expressing ra2 will be engineered to determine if ra2 has a similar function in dicots.